U.S. Pat. Nos. 5,031,495, 5,819,510, and 6,834,476 and U.S. published application 2002-23417 describe presses used to laminate together two foils that are either thermoplastic or that have confronting faces coated with thermally activatable adhesive. To this end there is typically a massive press frame having an upper traverse, a lower traverse, and several vertical tie rods fixing the two traverses together so that they cannot move relatively to each other. A central table or traverse can be reciprocated vertically on the tie rods between the upper and lower traversed.
The workpiece typically comprises an essentially flat and planar upper foil or sheet and a lower foil or sheet formed with an array of pockets or blisters that project downward and that are filled with some product. e.g. a foodstuff or medicament, to be encapsulated in the pocket by sealing the upper foil down against the lower foil around each pocket. Thus in the simplest system the upper traverse carries a heated upper die that has a planar lower face stationarily positioned immediately above the upper foil and the reciprocal table carries a lower die having a plurality of upwardly open recesses arrayed to fit around the pockets of the lower foil. When the lower die is pushed upward against the workpiece, it presses the two foils against the lower face of the upper die and seals them together.
With such an arrangement it is necessary to accurately feed the workpiece to the press, so that it is as close as is possible without overheating it to the upper die, but still out of contact therewith. Thus it the workpiece thickness changes or some other parameter is varied, it is necessary to meticulously readjust the equipment.